For example, exosomes can generate CAFs through the transmission of growth factors involved in fibroblast activation, such as TGF-β from bladder cancer cells that activates SMAD pathway in fibroblasts [25], or the transfer of BMP from gastric cancer cells that activates PI3K/AKT and MEK/ERK pathways in pericytes [26,27]. Here, TGFB1 is linked to urinary bladder cancer.